Magdalena Anguelova Ph.D. Student Advisor: Prof. Ferris Webster

1. in the The Ocean Climate What is a Greenhouse Effect? System 5 min. Magdalena AnguelovaPh.D. Student Advisor: Prof. Ferris Webster

2. The Living Planet Of all planets in our Solar system, Our Solar System only Earth has life as we know it. The reason? The natural greenhouse effect caused by the Earth’s atmosphere.

3. The Sun • The Sun is the major source of light and warmth that life on Earth needs. • The sun has a temperature of 6000 oC.

4. The Solar Spectrum Electromagnetic spectrum Medicine Broadcasting • At such a high temperature the solar emission peaks in the visible range. The visible range

5. The Earth Spectrum Electromagnetic spectrum • The average surface temperature of Earth is 15 oC (59 oF). Thus... • Earth emits in the far infrared (IR) range.

6. Greenhouse Effect • From the solar radiation at the top of the atmosphere A, • Only a part reaches the Earth surface B. • Earth absorbs part of B and warms. • Then Earth emits that heat as IR radiation C . • Atmospheric gases trap some of this IR radiation D, • and re-emit it back to Earth.

7. Greenhouse Effect • This is the natural greenhouse effect. • The natural greenhouse effect keeps the Earth’s surface about 33 oC (61 oF) warmer than it would be without the greenhouse effect.

8. The Atmosphere The atmosphere is thin as an onion skin. • The natural greenhouse effect is due to the presence of the atmosphere. • Without the atmosphere, the IR radiation emitted by Earth would escape to the space. Earth would be a frozen planet, just like Mars.

9. The Greenhouse Gases • Atmospheric gases trapping the IR radiation are naturally occurring. • These are: • Water vapor (H2O); • Carbon dioxide (CO2); • Methane (CH4); • Nitrous oxide (N2O).

10. Carbon Dioxide (CO2) • Sources: • Metabolic reactions in plants and animals; • Respiration. • Sinks: • Ocean; • Land vegetation.

11. Methane (CH4) • Powerful greenhouse gas: • Absorbs IR radiation 20 times more effectively than CO2; • But CH4 concentration is much less than CO2. • Sources -- biological processes in: • Herbivorous animals; • Wetlands and swamps. • Sinks: • Chemical reactions in the atmosphere; • Ocean.

12. Nitrous Oxide (N2O) • Involved in: • Greenhouse effect; • Ozone depletion. • Sources: • Bacterial processes in the ocean; • Termites; • Soil. • Sinks: chemical reaction with oxygen in the stratosphere.

13. Water vapor (H2O) • Of all natural greenhouse gases H2O is: • The most abundant; • The most important in creating the natural greenhouse effect.

14. Natural Concentrations • Naturally CO2, CH4, and N2O are in trace amounts compared to water vapor. • In a long run their amounts in the Earth's atmosphere remain relatively stable.

15. Climate Variability • 90 % of Earth’s history the climate has been warm, • A few degree warmer than today.

16. CO2 Variations • During climate swings, CO2 concentration changed too. • Ice cores show that CO2: • Decreased during glacial periods; • Increased in warm times.

17. CO2 in the Past Atmospheric CO2 from ice cores Changes no more than 4 %. Natural!

18. The Concern • Pristine Earth… • ...until about a century ago, • when concentrations of CO2, CH4, and N2O began to increase due to: • Industrialization, • Demand for energy, • Rising population, • Human settlement.

19. CO2 in the Last Century Atmospheric CO2 from ice cores Changes no more than 4 %. Natural! Changes about 20 %. Man-induced!

20. Enhanced Greenhouse Effect • Human activities lead to build-up of CO2, CH4, and N2O in excess of their natural amounts. • This may enhance the natural greenhouse effect. • The consequences may be dramatic.

21. Today CO2 increase is responsible for 71% of the enhanced greenhouse effect.

22. Today The End